class Phone:
    __is_5g_enable = False

    def __check_5g(self):
        if self.__is_5g_enable:
            print('5G开启!')
        else:
            print('5G关闭!使用4G网络!')

    def call_by_5g(self):
        self.__check_5g()
        print('正在通话中!')


phone = Phone()
phone.call_by_5g()